1. Field of the Invention
This invention relates to a method for purifying or refining sugar phosphates or their salts and more particularly to a method for purifying sugar phosphates or their salts by electrodialysis.
The term "electrodialysis" used herein is intended to mean a technique in which there is provided a multiple chamber-type dialyzing vessel which has cation exchanger membranes capable of passing cations and anion exchanger membranes capable of passing anions arranged alternately and is provided with electrodes at opposite ends of the vessel, and a direct current is passed across the electrodes to move anions toward the anode and cations toward the cathode.
2. Description of the Prior Art
Sugar phosphates are compounds present abundantly in living bodies and are known as being useful. For instance, glucose-1-phosphate is useful as an antibacterial agent for medicines, an antitumor agent (platinum complex) and a curing agent for heart diseases (amine salts). Glucose-6-phosphate is useful as an acute hemorrhage curing agent for low blood pressure patients or reagent for analyzing substances in living body such as, for example, a glucose-6-phosphate dehydrogenase, a glucose-6-phosphate esterase and the like.
Heretofore, various processes of preparing sugar phosphates are known, including, for example, a process in which a glucan and an orthophosphate are reacted in the presence of a phosphorylase to obtain glucose-1-phosphate [J. B. Summer et al, Arch. Biochem., 4, 11 (1944) and R. M. McCready et al, J. Am. Chem. Soc., 66, 560(1944)], a process of preparing glucose-6-phosphate by reaction between glucose and metaphosphoric acid or a polyphosphoric acid in the presence of a microorganism such as belonging to the Acromobacter (Japanese Patent Publication No. 58-32597), and a process of preparing glucose-6-phosphate by reaction between glucose and a polyphosphoric acid (Japanese Patent Publication No. 40-15172).
When, however, orthophosphates or polyphosphoric acid is used as a phosphorylating agent as in these processes, it is inevitable that orthophosphates or polyphosphoric acid be contained in the resultant sugar phosphates.
However, when large amounts of orthophosphates or polyphosphoric acid is contained in the sugar phosphates or their salts, unfavorable influences may be produced depending on the use, for instance, in case where the sugar phosphates or their salts are used as a medicine or a reagent for analysis of substances in the living body.
In general methods of separating a large amount of phosphoric acid or its salt from a mixture of sugar phosphates or their salts and phosphoric acid or its salt, phosphoric acid or its salt is insolubilized by conversion into Ba.sub.3 (PO.sub.4).sub.2, Mg.sub.3 (PO.sub.4).sub.2, Li.sub.3 PO.sub.4, MgNH.sub.4 PO.sub.4 and the like. These methods undesirably require the step of filtering the insolubilized phosphoric acid salts, thus making the process complicated and/or involving a loss of the sugar phosphates in the filter cake. Thus, these methods are not favorable as an industrial separation and purification method. In addition, a large amount of the phosphoric acid salts is wasted with a very poor economy.
Accordingly, there is a demand of the development of a purification method for the separation of sugar phosphates or their salts from phosphoric acid or its salt in which the phosphoric acid or its salt can be separated readily and in a re-utilizable form.